With the rapid development of the information industry, the wireless communication technology is faced with unprecedented challenges in the future. In the foreseeable future, the need for wireless data services in the world will keep high growth. According to a report from the International Telecommunication Union (ITU), wireless data services will increase at least 1000 times by 2020. In particular countries and regions, the figure may be even higher. In response to the unprecedented challenges, 5G communication technologies research has been extensively launched across the world.
In various potential technologies capable of enhancing spectrum efficiency, the new air interface access technology gradually gets attentions of academics and industry. Because the 5G communication system may be faced with more challenging application scenarios, the conventional modulation waveform and multiple access technology are faced with many challenges, such as more rigorous synchronization requirements, a shorter transmission delay and more fragmented spectrum resources. Based on above mentioned challenges, some more advanced waveforms are taken into account. A Filter Bank Multiple Carrier (FBMC) system has become one of the hotspots of the research. Because a prototype filter is used to perform pulse shaping on the transmission waveform, the transmission signal shows a variety of excellent characteristics, such as a lower requirement on time-frequency synchronization precision and higher time-frequency localization property. In addition, compared with conventional Orthogonal Frequency Domain Multiplexing (OFDM), the FBMC needs no extra Cyclic Prefix (CP), thus the FBMC possesses the higher spectrum efficiency. Based on above mentioned advantages, the FBMC and other possible multi-carrier modulation techniques are included in a technical report “IMT. Future Technology Trends” of the ITU.
However, in a system using the FBMC modulation, in order to obtain the maximal spectrum efficiency, the Offset Quadrature Amplitude Modulation (OQAM) technology is adopted. In the OQAM technology, there is a non-orthogonal relationship between adjacent carriers, that is, a carrier may interfere with an adjacent carrier. The interference may have a serious impact on channel estimation of the system, thus the system reliability will have a significant drop. Many existing methods are provided to resolve the interference problem, but the efficiency of the methods is low. In the description of the present disclosure, some existing methods will be illustrated, and it will be described in detail that how the technical solutions of the present disclosure improve the utilization of the carrier resource and reduce the interference to the reference signal, thus higher channel estimation and synchronization performance may be obtained.